ISO 3941:2026 Update – New Fire Class L Explained | Lithium Battery Fire Risk

The fire safety industry has witnessed a major update in 2026. The latest edition of ISO 3941 has officially introduced a new fire classification – Class L, specifically for Lithium-ion battery fires.

With the rapid use of electric vehicles, power banks, mobile phones, solar battery storage systems, and industrial lithium battery packs, this update is extremely important for Safety Officers, Fire & Safety students, and industries worldwide.

In this detailed guide, we will explain:

What is ISO 3941?
What changed in ISO 3941:2026?
What is Class L fire?
Why was Class L introduced?
Difference between Class D and Class L
How to control lithium battery fires?
What this means for safety professionals

What is ISO 3941?

ISO 3941 is an international standard that classifies fires based on the type of fuel involved.

🔥 Traditional Fire Classes Under ISO 3941

Class A – Solid combustible materials (wood, paper, cloth, plastic)

Class B – Flammable liquids (petrol, diesel, solvents)

Class C – Flammable gases (LPG, propane, methane)

Class D – Combustible metals (magnesium, sodium, aluminum powder)

Class F – Cooking oils and fats

⚠️ Important: ISO does not include “Class E” (electrical fire). Electrical fire is considered a source of ignition, not a fuel class.

What is New in ISO 3941:2026?

The 2026 edition has introduced:

🆕 Class L – Lithium-Ion Battery Fires

This is a major development because lithium-ion battery fires behave differently from traditional fires.

What is Class L Fire?

Definition (Simple & Professional)

Class L fire refers to fires involving Lithium-ion cells and battery systems where no free metallic lithium is present.

These fires occur in:

Electric Vehicles (EVs)
Mobile phones
Power banks
Laptops
Solar energy storage systems
Industrial battery banks

Why Was Class L Introduced?

Lithium-ion battery fires are increasing worldwide due to:

Battery overheating
Short circuits
Overcharging
Physical damage
Manufacturing defects
Thermal runaway

What is Thermal Runaway?

Thermal runaway is a chain reaction inside a lithium battery where:

Heat increases rapidly
Flammable gases are released
The battery may explode
Re-ignition can occur even after extinguishing

This behavior is very different from Class A, B, or D fires.

Difference Between Class D and Class L Fire

Many safety professionals confuse Class D and Class L.

Feature Class D Class L

Fuel Type Combustible metals Lithium-ion batteries
Metallic Lithium Yes No free metallic lithium
Reaction Type Metal combustion Electrochemical thermal runaway
Re-ignition Risk Moderate Very High
Cooling Required Limited Continuous Cooling Required

👉 Class L is not a metal fire like magnesium or sodium.

Why Lithium Battery Fires Are Dangerous?

1. Very high temperature (can exceed 1000°C)

2. Explosion risk

3. Toxic gas release (HF, CO)

4. Difficult to extinguish

5. Re-ignition after hours

This is why ISO officially created a separate classification.

How to Extinguish Class L Fire?

There is no universal solution, but generally:

Recommended Control Measures:

Large amount of water for cooling
Specialized lithium fire suppression agents
Immersion containers (for small battery packs)
Battery fire blankets (for EVs)
Isolation and monitoring

⚠️ Normal ABC extinguisher is not sufficient for large lithium battery fires.

What This Means for Safety Officers & Industries

If you are:

A Safety Officer
A Fire & Safety Student
Working in EV industry
Working in solar energy sector
Handling warehouse battery storage

You must update:

Fire Risk Assessment
Emergency Response Plan
Firefighting equipment
Training modules
HIRA and JSA documentation

This update is very important for modern industrial safety planning.

ISO 3941:2026 update

Class L fire meaning

Lithium battery fire classification

New fire class 2026

Lithium-ion fire risk

How to extinguish lithium battery fire

Difference between Class D and Class L

Final Conclusion

The ISO 3941:2026 update marks a significant milestone in fire safety standards. The introduction of Class L fire recognizes the growing global risk posed by lithium-ion batteries.

As electric vehicles and energy storage systems continue to expand, understanding Class L fire is no longer optional — it is essential for every safety professional.

Frequently Asked Questions (FAQ) – ISO 3941:2026 & Class L Fire

1️⃣ What is ISO 3941?

ISO 3941 is an international standard that classifies fires based on the type of fuel involved, such as solids, liquids, gases, metals, cooking oils, and now lithium-ion batteries.

2️⃣ What is new in ISO 3941:2026?

The 2026 edition introduced a new fire class – Class L, specifically for lithium-ion battery fires.

3️⃣ What is Class L fire?

Class L fire refers to fires involving lithium-ion cells and battery systems where no free metallic lithium is present.

These include:

Electric vehicles (EVs)

Mobile phones

Power banks

Solar battery storage systems

4️⃣ Why was Class L introduced?

Because lithium-ion battery fires:

Can undergo thermal runaway

Reach extremely high temperatures

Release toxic gases

Have high re-ignition risk

Traditional fire classes did not properly address these unique risks.

5️⃣ Is Class L the same as Class D?

No.

Class D = combustible metal fires (magnesium, sodium)

Class L = lithium-ion battery fires (electrochemical reaction, not metal combustion)

They require different control strategies.

6️⃣ Does ISO include Class E (electrical fire)?

No. ISO 3941 does not include Class E.

Electrical fire is considered a source of ignition, not a fuel class under ISO classification.

7️⃣ Can ABC extinguisher control Class L fire?

For small lithium battery fires, it may suppress flames temporarily.

However, large lithium-ion battery fires require:

Continuous cooling (large water application)

Specialized lithium fire suppression systems

Proper isolation and monitoring

8️⃣ What industries are affected by Class L fire classification?

EV manufacturing

Solar energy storage

Warehousing & logistics

Oil & Gas facilities using battery systems

Industrial power backup systems

9️⃣ What is thermal runaway in lithium batteries?

Thermal runaway is a chain reaction where battery temperature rapidly increases, causing fire, explosion, and possible re-ignition even after extinguishing.

🔟 Why should Safety Officers know about Class L fire?

Because modern industries widely use lithium-ion batteries. Risk Assessment, ERP, HIRA, and firefighting planning must now consider Class L fire hazards.